The Tengo Language

Tengo is a small, dynamic, fast, secure script language for Go.

Tengo is fast and secure because it's compiled/executed as bytecode on stack-based VM that's written in native Go.

/* The Tengo Language */
fmt := import("fmt")

each := func(seq, fn) {
    for x in seq { fn(x) }
}

sum := func(init, seq) {
    each(seq, func(x) { init += x })
    return init
}

fmt.println(sum(0, [1, 2, 3]))   // "6"
fmt.println(sum("", [1, 2, 3]))  // "123"

Test this Tengo code in the Tengo Playground

Features

• Simple and highly readable Syntax
• Dynamic typing with type coercion
• Higher-order functions and closures
• Immutable values
• Securely Embeddable and Extensible
• Compiler/runtime written in native Go (no external deps or cgo)
• Executable as a standalone language / REPL
• Use cases: rules engine, state machine, data pipeline, transpiler

Benchmark

fib(35): Fibonacci(35)
fibt(35): tail-call version of Fibonacci(35)
Go does not read the source code from file, while all other cases do_
_ See here for commands/codes used

Quick Start

go get github.com/d5/tengo/v2

A simple Go example code that compiles/runs Tengo script code with some input/output values:

package main

import (
    "context"
    "fmt"

    "github.com/d5/tengo/v2"
)

func main() {
    // create a new Script instance
    script := tengo.NewScript([]byte(
`each := func(seq, fn) {
    for x in seq { fn(x) }
}

sum := 0
mul := 1
each([a, b, c, d], func(x) {
    sum += x
    mul *= x
})`))

    // set values
    _ = script.Add("a", 1)
    _ = script.Add("b", 9)
    _ = script.Add("c", 8)
    _ = script.Add("d", 4)

    // run the script
    compiled, err := script.RunContext(context.Background())
    if err != nil {
        panic(err)
    }

    // retrieve values
    sum := compiled.Get("sum")
    mul := compiled.Get("mul")
    fmt.Println(sum, mul) // "22 288"
}

Or, if you need to evaluate a simple expression, you can use Eval function instead:

res, err := tengo.Eval(ctx,
    `input ? "success" : "fail"`,
    map[string]interface{}{"input": 1})
if err != nil {
    panic(err)
}
fmt.Println(res) // "success"

References

• Language Syntax
• Object Types
• Runtime Types and Operators
• Builtin Functions
• Interoperability
• Tengo CLI
• Standard Library
• Syntax Highlighters: VSCode, Atom, Vim
• Why the name Tengo? It's from 1Q84.